Hi Dick This is carried over from days of old. You are corect about the saturation except in this case the Line feed coils do form part of a transformer device. Usually there are two (200 ohm approx) feed coils on a relay former plus a transformer winding. Other types of relay feed rely on a series capacitive coupling (i.e. Stone Bridge).
The transformer arrangement is (was I mean) used in the UK on PABX feeds as a means of injecting progress tones etc. Cheers: Bill Ellingford ---------- From: Dick Shultz[SMTP:[email protected]] Sent: 15 March 1999 22:20 To: [email protected] Subject: RE: TBR 21- 60 mA max. loop current Joe, Bill, TREG, Something about the explanation attributed to the French smells fishy to me. If I remember correctly, a saturated inductor loses its reactive component and becomes purely resistive with no ac attenuation. If the reason attributed to the French were correct, I'd could get rich just saturating ferrites and selling perfect EMI filters in little boxes with dc power inputs. Maybe what was meant was that the transformers saturate. That kills ac coupling real well. Seems odd to be using a wet design in a modern CO line card, though. Maybe they went out with the step-by-steps and the requirement is a holdover from antiquity, as alleged. Dick Shultz On 3/15/99 7:45 AM Bill Ellingford <[email protected]> said >Hi Treg > snip > >I Understand that the French PTT say that the Feed inductors / relay >coils used in their network saturate at 60mA +, when saturated no ac is >passed so transmission becomes highly attenuated. This was too powerful >an argument for allowing current to exceed 60mA in the TBR / CTR. > >Cheers: Bill Ellingford > >. > big snip here
<<application/ms-tnef>>
